Ask HN: Can we kill the receipt?

I'm getting pretty frustrated with having to track tiny pieces of paper for expense reports, and, personally, I hate that even if I tell the clerk I don't want a receipt, it still prints off just for them to throw it away and kill some trees.

Is there a reason why terrible little pieces of paper with disappearing ink are still necessary to transacting business?

I appreciate that merchant services like Square are doing something about this. However, as a consumer, I have no control over which merchants care to implement it. Also, there has to be a better, more automatic identifier we can assign that will send a receipt without having to enter an email address every single time. What if it were possible to send a receipt automatically by scanning a QR code on the back of the credit card, or maybe in a phone app, or both? What if it were just a sticker you could attach to anything to be scanned at the register?

I'm sure the technical challenges (and maybe regulatory?) to solving this problem are enormous, but it's so, so frustrating to me that I'd be willing to find out how to make it happen.